Detailed functional morphological investigations of Mekong River hydrobioid taxa will continue along with detailed ecological assessments using techniques of multivariate analysis. It is essential to complete the analysis-in-progress of ecological data involving community structure, microhabitats, sympatry, and diversity in relationship to Mekong Schistosoma and the distribution of the snail host, Tricula aperta. Finding that a species of Tricula transmits the Mekong Schistosoma sp. is a major new discovery. Data on T. aperta, Mekong hydrobioids thus far studied, and related Pomatiopsine snails (which include Oncomelania) have led to a hypothesis on the origin and evolution of Asian Schistosoma involving over 100 million years time and introduction to Asia via the Indian Plate. Phylogenetic assessments using classical means and new techniques of multivariate analysis with ordination by non-metric multidimensional scaling have shown that of 1000 species of hydrobioid snails (world-wide) the capacity to transmit Asian Schistosoma infecting man is restricted to the family Pomatiopsidae, the subfamily Pomatiopsinae, the tribe Triculini of the Triculinae. Emphasis (in new work) is now placed on studying Tricula and closely related taxa using functional morphology, microanatomy, and ecological parameters. One test of the hypothesis on the origin of Asian Schistosoma is to study the little known Tomichia complex of S. Africa which has species seemingly related to both Oncomelania and Tricula. Also, Tricula of India, China, and the Philippines are known by name and shell only. Pertinent to testing the hypothesis is an analysis of so-called Oncomelania brasiliensis Rey and related taxa in Brazil.